Size determining mechanism for automatic machines



H. L. BLOOD Aug. 11, 1936.-

SIZE DETERMINING MECHANISM FOR AUT OMATIC MACHINES Filed Dec. 31, 1932 3 Sheets-Sheet 1 aw V HaRold Blbod Aug. 11, 1936. H. L. BLOOD 2,050,261

SIZE DETERMINING MECHANISM FOR AUTOMATIC mcnmns Filed D 1932 :5 Sheets-Sheet 2 as 3mm Homold. IMBI QCL H. 1.. BLOOD 2,050,261

SIZE DETERMINING MECHANISM FOR AUTOMATIC MACHINES Aug. 11, 1936.

3 Sheets-Sheet 3 Filed Dec. 31, 1932 awe/(m HCROId. L.B|ood Patented Aug. 11, 1936 UNITED STATES PATENT OFFICE SIZE DETERMINING MECHANISM FOR AUTOMATIC MACHINES Harold L. Blood, Worcester, Mass assignor to The Heald Machine Company,

Worcester,

23 Claims.

The present invention relates to automatic machines for the reduction of workpieces to a predetermined size, and although in certain of its aspects it is applicable to various types of automatic machines, its particular utility, as will hereinafter appear,"is in connection with machines for treating, as by a cutting operation, the internal surfaces of sleeves, gears, bushings and like articles.

1'0 In prior constructions of automatic machines 'of this character, the size of the workpiece being operated upon is determined either by a gage mechanism of the type shown in the McDonough Reissue Patent No. 16,141,- issued August 11, 1925,

15 a later construction of the same type being shown in the Kempton and Gallimore Patent No. 1,731,- 719, issued October 15, 1929, or by the movement of the crossfeed mechanism which causes the cutting tool to cut progressively deeper and deeper 29 into the surface of the workpiece, as shown in the Guild Patent No. 1,682,672, granted August 28,1928.

In the McDonough and Kempton and Gallimore grinding machine constructions, the gage member 25 is reciprocated relative to the workpiece, and the grinding operation is interrupted when the workpiece is ground to such a size that the gage may enter the bore therein. While a gaging mechanism of the above indicated character is entirely 30 satisfactory in operation, it has been found that the continued hammering action of a gage against the end of successive workpieces before a given workpiece reaches the predetermined size,

in addition to the wear on a gage as it enters within the bore of the workpiece, will impair the accuracy of the gage, necessitating inspection and replacement thereof in order to procure successive workpieces which are reduced consistently to a predetermined size.

49 In a grinding machine construction of. the type disclosed'in the Guild patent, the size of the workpieces is controlled by the movement of the crossfeed mechanism which operates to terminate the grinding operation when the cutting surface of the grinding wheel reaches a predetermined vertical plane during the crossfeed movement. The location of this plane is determined by a dressing tool which operates during each grinding operation to maintain the surface of the grinding 50 wheel smooth and in the desired position relative to said plane, said dressing operation resulting in a reduction in diameter of the grinding wheel, which is compensated for by a transverse compensatory movement of the grinding wheel rela- 55 tive to the workholding member to cause said wheel, during successive grinding operations, to move into the-above noted predetermined vertical plane before the grinding operation is terminated. Although machines of this construction are also entirely satisfactory in operation, the in- 5 equalities inherent in grinding wheels and the necessarily involved construction and operation of the machine are such that frequent inspections and adjustments must be made in order that successive workpieces shall all be reduced to the same desired size.

The principal object of the present invention is to provide a novel arrangement for determining the size of a workpiece which incorporates the advantages of the above constructions without incorporating any of the disadvantages thereof. According to the present invention, the size of the workpiece is automatically determined by utilizing variations in the impedance of an electrical circuit to control the grinding operation, such variations of impedance resulting from either removal of material from the workpiece,

or the approach of the grinding Wheel to a predetermined plane. Since the impedance of an electrical circuit is a combined function of its inductance and capacity, the invention contemplates the utilization of variations of either the inductance or capacity in the control or detecting circuit to determine the final size of a workpiece. In carrying out the invention, the use of gages that actually contact with the workpiece is entirely eliminated, as is also the use of complicated mechanism associated with the grinding wheel as heretofore, all as will hereinafter appear from the following detailed description taken in connection with the accompanying drawings, in

which:-

Fig. 1 is a front elevation of an internal grinding machine embodying, the invention, with a portion of the workhead in section to show the construction of an inductive gaging member cooperating with the workpiece.

Fig. 2 is a fragmentary plan view showing a different form of inductive gaging member.

Fig. 3 is a view in side elevation of the parts shown in Fig. 2.

Fig. 4 is a fragmentary sectional view showing a still different form of inductive gaging member cooperating with the grinding wheel.

Fig. 5 is a wiring diagram, illustrating automatic control of the machine through variations of inductance.

Fig. 6 is a wiring diagram similar to Fig. 5, illustrating the parts in different positions.

Fig. 7 is a wiring diagram, illustrating a modified form of inductance control.

-Fig. 8 is a fragmentary sectional view of a portion of the workhead and grinding wheel showing a condenser type of gaging member associated with the workpiece.

Fig. 9 is a fragmentary sectional view illustrating a condenser type of gaging member associated with the grinding wheel.

Fig. 10 is a wiring diagram illustrating automatic control of the machine through variations of capacity.

Fig. 11 is a wiring diagram illustrating a modifled form of capacity control.

Like reference characters refer to like parts in the different figures.

Referring first to Fig. 1, the machine provides the usual reciprocatory table I provided in an internal grinding machine; either the grinding wheel or the work to be ground may be carried on said table, the reciprocations of the latter operating in either case to produce a relative movement between said grinding wheel and workpiece. In the construction shown, the table I supports and carries a wheelhead 2, and the work to be operated upon is held in a workhead 8, the latter being carried by a bridge 4 which spans the slideways, not shown, provided by the machine frame, for the back and forth movement of the table I. A grinding wheel 5 is mounted on a spindle 6 journaled in the wheel head 2 and a workpiece a is mounted in a suitable workholding chuck or other clamping device I journaled in the workhead.

The back and forth movement of the table I to cause the wheel 5 to make the required traverse of the workpiece a may be procured in any well known manner, as by the use of the fluid pressure controlling and reversing mechanism, forming the subject matter of the Heald 8: Guild Patent No. 1,582,468, granted April 27, 1926. Such mechanism forms no part of the present invention; it is suflicient to note that the drivin means employed procures the reversal of the table at each end of its normal grinding stroke by the use of spaced adjustable dogs 8 and 9 carried by the table I and adapted alternately to engage and to move a reversing member I0. The latter during the grinding operation, when the grinding wheel 5 is moving back and forth within the workpiece a. is situated between said dogs 8 and 9 in position to be alternately struck by said dogs and, by its consequent movement, effects the reversals of the table I. The grinding wheel 5 is rotated'at a high speed in any suitable manner and the workholding member I is also rotated at a somewhat slower speed by a belt drive, as will hereinafter appear.

The wheelhead 2 of the machine is mounted on a cross-slide II which is arranged to have a transverse movement onsuitable ways, not

' type disclosed in the above noted Guild Patent No. 1,682,672 to procure a feeding movement of the grinding wheel 5 to cause said wheel to cut progressively deeperzand deeper into the workpiece a; for the purpose of the present invention, it is sufflcient to note that a ratchet wheel, not shown, is engaged by a pawl I8 which is actuated in response to the reciprocation of the carriage I, thereby procuring rotation of said crossfeed shaft I2 carrying the grinding wheel transversely against the surface of the workpiece.

In the previous operation of grinding machines of the type shown and described in the aforesaid Patent No. 1,682,672, the grinding operation is interrupted before the workpiece reaches predetermined finished size, the interruption occurring in response to the movement of the,

crossfeed mechanism to procure separation of the grinding wheel from the workpiece, in order that a dressing operation may be performed on the wheel. After the dressing operation has been performed on the wheel, the grinding operation is resumed until the workpiece is ground to a predetermined finished size, whereupon the grinding operation is brought to a close by a second separation of the grinding wheel from the work in response to the crossfeed mechanism. And since the present invention also contemplates both an initial separation of the grinding wheel from the workpiece for truing, followed by resumption of the grinding to complete the work, there is shown in Fig. 1 as an illustrative embodiment of the invention certain of the same wheel controlling mechanism described in the aforesaid Patent No. 1,682,672, to which mechanism automatic control through variations of electrical impedance has been applied.

- As previously pointed out, in normal operation of the machine, back and forth movement is imparted to the table I by the cooperation of the spaced dogs 8 and 9 with the reversing member I0, and for the purpose of automatically interrupting the grinding operation on the workpiece and separating the wheel for the dressing operation, the machine provides a lever I4 pivotally mounted on a shaft I5, as shown in the broken away portion of Fig. 1. The lever I4 has integral therewith a magnetic armature I6 dis- 7 posed in operative relation with respect to the core of an electromagnet II, the unbalanced weight of the lever I4 tending to maintain the armature I 6 spaced from the end of the electromagnet core "as long as the electromagnet I! remains in a deenergized condition. Upon'energization of the electromagnet H in a manner hereinafter .-dcscribed, attraction of the armature I8 imparts upward movement to the lever I4 and causes the latter to lift a latch I8, assuming that the grinding wheelhead 2 is then in its left hand position with the grinding wheel 5 within the workpiece a.

The latch I8 extends between a block I9 carrying the left hand table dog 8, which block I8 is capable of free sliding movement on the table I, and a stationary block 28 on which the latch I8 is pivotally mounted at 2I. Under normal conditions, the block I9 is held in spaced relation tow the stationary block 28 by the latch I8, but when the lever I 4 is elevated as described above, the latch I8 releases the block I8 and subsequent right hand travel of the table I involves relative sliding movement between the table and the block I8, owing to the obs ction which the reversing member III impos s against the left hand table dog 8. Continued travel of the table I finally brings the stationary block 28 up against the thenslidable block I9, whereupon the dog 8 becomesimmovably supported for shifting the reversing member III to procure reversal of the table. The 'above described sliding movement of the block I 8 on the table I, when released by the latch I 8, results in an amplified right hand lowing the amplified dressing stroke, the revers ing dog 8 is restored to its normal position by a ,resiliently supported lug 23 which engages the block I9, and as the table moves to the'left, ofi"ers enough resistance to movement of the block I9 with the table to detain the block until the latch I 8 is restored to its normal position in which it positively holds the block l9 separated from the block 20. On the above noted amplified right hand dressing, stroke of the table I,- in order to prevent a repetition of the dressing stroke, an arm 24 mounted on the latch pivot 2| strikes a lug 25 of a switch member 26 pivotally mounted on an axis parallel to the shaft l5 of the lever I4, thereby turning the switch member 26 into the position shown to break the circuit through the electromagnet I1 and release the lever I4, as will be hereinafter more fully described;

Upon the resumption oi the grinding operation after dressing of the wheel as described above, the normal back and forthmovement of the table continues until the work is reduced to a predetermined finished size, whereupon the grinding operation is brought to a close by a second separation of the grinding wheel from the work in response to the electric impedance control control of the present invention. For the purpose of obtaining a final run' out of the table I into the position shown in Fig. 1, there is provided a second lever 21 mounted on the same shaft I5 as the lever I4, the lever 21 having integral therewith an armature 28 responsive to an electromagnet 29, as shown in Fig. 5. Normally, the unbalanced weight of the lever 21 maintains the armature 28 away from the core of the electromagnet 29 while the latter is in a deenergized condition, and such is the condition of affairs during the grinding operation. Upon energization of the electromagnet 29 in the manner hereinafter described, the lever 21 is raised to move' its upper end into the path of the left hand table dog 8, while the table is in its left hand position. Since the table dog 8 is pivotally mounted on its block 53, right hand movement of the tableafter elevation of the lever 21 results in lifting of the dog 8 so that it is carried clear of the reversing member ID. Therefore, the table I is not reversed, but continues its movement to the right carrying the grinding wheel 5 out of the workmiece a, the table being brought to a full stop by any suitable means, such as is shown in the aforesaid Heald & Guild Patent No. 1,582,468. The return of the table I to the working position from the fully withdrawn position of Fig. 1 is effected by the shifting of a hand lever 30 operatively connected to the reversing member ID and on the left hand movement of the table an arm 3| also mounted on the pivot 2| strikes a second lug 32 on the movable switch member 26, thereby turning the switch member in a position to disconnect the electromagnet 29 from its source. This turning movement of the switch member 26 upon the initiation of another grinding cycle restores the switch member to the position shown in Fig. 5 in readiness for the energization, at the proper time in the grinding of the next workpiece, of the electromagnet I'l controlling the wheel dressing operation.

The above described mechanism for mechanically controlling the movements of the table I carrying the grinding wheel is more fully described in the above mentioned Guild Patent No. 1,682,672, and therefore forms no part of the present invention per se; the present invention as previously pointed out, involving the attainment in connection with the above described or similar grinding machine instrumentalities, of automatic size determining mechanism primarly responsive to variations of the impedance of an electrical circuit resulting from either removal of material from the workpiece, or the approach of the grinding wheel to a predetermined plane. In other words, the table controlling mechanism described above with reference to Fig. 1 is merely an illustrative embodiment of the manner in which any one of the several forms of impedance control, next to be described, can be applied to .a grinding machine of the character shown.

As best shown in the sectional portion of Fig. 1, one form 01 the impedance control contemplated by the' present invention embodies the use of an exploring or gaging coil 33 mounted on a magnetic core 34 and adapted to be moved into and out pf the workpiece a. in timed relation with the reciprocatory movement of the grinding wheel 5. To this end, the coil 33 and its core 34 are -mou.nted ona sleeve 35 movable longitudinally within the hollow spindle 36 carrying the workholding chuck I, the spindle 36 being journaled in,

bearings 31 provided by the workhead 3 with a pulley 38 serving to rotatably drive the spindle 36. The sleeve 35 carrying the coil 33 projects beyond the rear end of the workhead spindle 35 and is clamped by a. bracket 39 adapted to have a reciprocatory motion imparted thereto by end of the table I, shown in dotted lines.

The bracket 39 carrying the sleeve 3515 normally urged in the direction of the workpiece a by means of a spring. 40, a stud 4I adjustable in a bushing 42 carried by the bracket 39 servingto limit movement of the sleeve 35 by its engagement with a stop lug 43, in which position a. magnetic disk 34a; forming part of the core of the coil 33 is disposed within the inner end of the workpiece a. On each left hand movement of the grinding wheel 5 during the grinding .the end of each complete reciprocation of the grinding wheel 5. Upon withdrawal of the grinding wheel from the workpiece a, the fixed s'top lug 43 limits the movement of the magnetic disk 34 into the workpiece, the adjustable stud 4| afiording means whereby the extent to which the disk 34m enters workpieces of different lengths may be controlled.

Leads 44 extend from the gaging coil 33 through the sleeve 35 to terminals $5 on the bracket 39 and, as shown in Fig. 5, the coil terminals 45 are connected across the secondary winding 45 of a transformer. The primary winding 41 has one terminal connected directly to a source of, alternating current indicated at 48, while the other terminal thereof is connected to the source 48 in series with windings 49 and 50 of relays adapted to control the energization of 'stop 52 by a spring 53.

the electromagnets I1 and 29, in accordance with variations of the inductance in the closed electrical circuit comprising the gaging coil 33 and the secondary winding 46.

To this end, one terminal of the electromagnet I! is connected to the movable contact 5| under the control of the relay winding 49, the contact 5| being normally held against a fixed The stationary contact 54 of this relay is adapted to be connected to ground, as indicated at 55, by relatively movable contacts 56 and 51, the contact 56 being mounted on the table I so as to engage the stationary contact 51 just as the magnetic disk 34a enters the workpiece. The other terminal of electromagnet I1 is connected to a stationary contact 68 engaged by the movable switch member 26 in the position shown in Fig. 5; the movable contact member 26 being in turn connected to the supply generator 59, which is also grounded as indicated at 55a. With the circuit connections just described, it is obvious that the electromagnet I! will remain in a deenergized condition until its circuit is closed by engagement of the relatively movable relay contacts 5| and 54, in response to energization of the relay winding 49.

The terminals of the electromagnet 29 are similarly connected to-the movable contact 66 under the control of relay winding 56 and to a stationary contact 6| adapted to be engaged by the pivoted switch member 26 in the position shown in dotted lines in Fig. 6. The movable relay contact 66 is normally maintained by .a spring 62 against a stop 63, so that the circuit of the electromagnet 29 is adapted to be completed through the table ground 55 only when the relay winding 56 .is energized to an extent sufficient to move the contact 66 into engagement with the stationary contact 64.

As previously pointed out, each right hand movement of the grinding wheel 5 in contact with the workpiece a is accompanied by entrance of the magnetic disk 34a of the gaging coil 33 into the workpiece, and as the workpiece itself provides a closed magnetic circuit surrounding the coil 33 and its core, the inductance of the coil circuit is at a maximum value, with the parts in the position of Fig. 5. This condition of high inductance is particularly pronounced at the beginning of the grinding cycle on a given workpiece, since the diameter of the magnetic disk 34a is but very slightly less than the unreduced diameter of the workpiece 0. Consequently, each time the gaging coil 33 and disk 34a enter the workpiece a during the early stages of the grinding operation, the inductance of the closed circuit through the coil 33 is so high that very little current flows through the secondary winding 46. As a result, an even smaller current flows through the primary winding 41 in circuit with the relay windings 49 and 56, and the movable contact members SI and 66 of the relays are held in the position shown in Fig. 5, in which both electromagnets l1 and 29 are deenergized.

As the grinding operation proceeds and the diameter of the workpiece a increases, the inductance of the circuit of the gaging coil 33 will decrease as the air gap between the periphery of the disk 34:: and the workpiece a gradually increases. Therefore, after a number of reciprocations of the grinding wheel 5 to reduce the workpiece to roughing size, the inductance of the gaging coil circuit will be reduced to such an extent that enough current will flow through the relay winding 49 to move the contact 5| against stationary contact 54 as the disk 34a enters the workpiece. Since as previously pointed out, the table contact 56 is in engagement with the stationary contact 51 at this moment, the electromagnet I! will be energized as indicated in Fig. 6, thereby raising the lever l4. Since the lever I4 is raised by energization of the electromagnet l1, after the grinding wheel 5 has started on its right hand movement, the resulting lifting of the latch l8 releases the block I9 and renders the table dog 8 ineiiective to turn the reversing member ID until after the table I has run out far enough to withdraw the grinding wheel 5 from the work for truing by the *dressing tool 22, as previously described. The

circuit of the electromagnet H is broken as the grinding wheel 5 is withdrawn, clue to the engagement of the lug 25 on the movable switch member 26 by the arm 24, thereby disconnecting the contact 58 from the generator 59. With the switch member 26 in engagement with the contact 6| leading to the electromagnet 29, as indicated in dotted line in Fig. 6, the circuit of the electromagnet 29 is in condition to be completed, upon closure of the movable contact 66 by the relay winding 50, as will next be described.

Upon resumption of the grinding operation following truing of the wheel 5, removal of additional material from the workpiece a still further increases the air gap between the peripheries of the workpiece and the gaging disk 34a, thereby permitting increased current to flow in the circuit of the primary winding 41. The relay winding 56 and the pull of the spring 62 are so proportioned that the winding 56 will be energized sumciently to attract the movable contact member 66 when the diameter of the work has been reduced to the predetermined finished size. Engagement of the movable contact 66 with the stationary contact 64 of this relay energizes the electromagnet 29, thereby raising the lever 21 into the path of movement of the left hand table dog 8. Consequently, the dog 8 clears the reversing member ID and the right hand movement of electromagnet l1 and the gaging coil resumesv control of the grinding cycle in the manner previously described. In order to prevent the relay windings 49 and 56 from being energized each time that the disk ,34a is withdrawn from the workpiece, a pair of spaced contacts 65 are provided in the circuit of the primary winding 41, which contacts are adapted to he bridged by a plate 66 on the table The plate 66 completes the circuit of the primary winding 41 just in advance of the entry of the disk 34a into the workpiece a,

so that the relay windings 49 and 56 are energized only when the inductance of the secondary circuit is reduced to the predetermined value. Since the circuits of the electromagnets l1 and 29 shown in Figs. 5 and 6 can be completed only when the table controlled contacts 56 and 51 are in engagement, and since energization of the primary control circuit occurs only just in advance of inductive gaging, the possibility of the movable relay contacts and 60 being held up by residual magnetism to cause premature operation of the wheel separating instrumentalities is substantially eliminated.

Referring now to Figs. 2 and 3, there is shown a modified form of inductance gage in which the gaging coil 33' is mounted on a core 61 movable with the table I. The core 61 extends upwardly and laterally, and terminates in a finger 68 extending parallel to the axis of the grinding wheel 5. The gaging finger 68 is spaced from the wheel 5 in a horizontal plane and is adapted to enter the workpiece a with the wheel 5. Assuming that the terminals of the gaging coil 33' are connected in a closed circuit with the secondary winding 46, as shown in Fig. 5, it is evident that when the finger 68 enters within the workpiece, the inductance of the secondary circuit will have a high value determined by the initial gap between the finger 68 and the unreduced workpiece. As the internal diameter of the workpiece a increases, the inductance of the secondary circuit will decrease in the manner previously described with reference to Figs. 1, 5 and 6, so as to automatically cause first the separation of the grinding wheel from the workpiece, for truing of the wheel, and finally the run out of the table when the work reaches a predetermined finished size.

In the previously described control of the. grinding operations, variations of inductance resulting from removal of material from the workpiece have been utilized, but as previously pointed out, the invention also contemplates utilization of the actual approach of the periphery of the grinding wheel to a predetermined vertical plane by the crossfeed movement to obtain the desired variations of inductance values. In Fig. 4 a gaging coil 33" is shown as mounted on a fixed magnetic core 69 with a solid head 70 of magnetic material carried by an arm 1|, so that the head is held close to the magnetic core 69. The head supporting arm H is carried by one end of a resilient member 12 shown as a leaf spring, with the other end of the member 12 received in a bracket 13 which extends upwardly and supports the core 59. The bracket 13 provides a foot portion 13a movable on a fixed guideway Ht provided by the machine base, with an adjusting screw 15 adapted to shift the bracket 73 laterally on the guid-eway M, with respect to the axis of the grinding wheel 5.

Normally, with the parts in the position shown in Fig. 4, that is at the start of the grinding operation, the resilient member 12 extends substantially horizontally, so that the arm I! maintains the head 10 in a position in which it is nearly in engagement with the end of the core 89. Assuming then that the terminals of the gaging coil 33" are connected in a closed circuit with the secondary winding 46 as shown in Fig. 5, it is evident that the inductance of the secondary circuit will have such a high value that the windings 49 and 50 will remain in a deenergized con dition. This condition of affairs obtains at the start of the grinding operation and continues as long as there is a gap between the periphery of the grinding wheel 5 and the rounded surface of a diamond I6, or other inset of hard material, carried by the lower extremity of the arm 'll below the plane of the resilient member 12.

As the grinding proceeds, each operation of the crossfeed mechanism brings the periphery of the grinding wheel inearer the surface of the diamond J6 and the bracket 13 carrying the arm II is so set that when the workpiece has been reduced to the roughing size, the next succeeding crossfeed of the wheelhead will cause the periphery of the wheel 5 to engage the rounded surface of the diamond 16 When this occurs, the lower end of the arm H is depressed, due to the fiexure of the member 12, thereby swinging the head 10 of the arm 1| away from the core 69. Dueto the relativelymuch greater distance between the head 10 and the member I2, as compared to the distance between the diamond 16 and the member 72, a very slight deflection of the member 12 will move the head 10 a considerable distance away from the core. When this occurs, the inductance of the secondary circuit will decrease to such an extent as to automatically cause first, separation of the grinding wheel from the workpiece for truing of the wheel in response to energization of the electromagnet l1, and finally the run out of the table in response to energization of the electromagnet 29 when the wheel '5 reaches its position for the final cut.

Referring now to Fig. '7, the gaging coil 33' is shown connected in the grid circuit of the thyratrqn tube l1, so that the output of the tube ll will vary inaccordance with variations in the inductance of the gaging coil circuit, in the manner previously described. The tube 11 is of a well known type and is adapted to be energized from the primary winding '38 of a transformer T connected to an alternating current source 19,

with one secondary winding 80a adapted to mapress a suitable voltage on the plate of the tube 11, while another secondary winding 80b impresses a suitable voltageon the filament of the tube 11. The primary winding 8B of the grid transformer T is connected across a portion of the secondary winding 80a, while the terminals of the gaging coil 33' are connected in parallel with the grid transformer winding 8i across an-. other portion of the secondary winding 80a, including more turns than that portion of winding 80a which impresses a voltage on the primary winding 8| 'of the grid transformer T'. With the above described connections, the voltage of the output of the tube T! will be responsive to variations in the impedance of the closed circuit including the gaging coil 33', and fluctuations of the tube output voltage are'utilized to control energization of the electromagnets H and 29, as will now be described.

To this end, relay windings 39 and 50 are connected in series across one terminal of the secondary winding 82 of the grid transformer T and a terminal of the primary winding 8|. With the relay windings 49' and 50' in a deenergized condition as shown in Fig. 7, movable contacts 83 and. 84 connected to the electromagnet l l and 29, respectively, are yieldingly held in engagement with stationary contacts 85 and 86.-

The stationary contacts 85 and 86 are in turn connected in parallel with stationary contact 51 adapted to be engaged by the table carried grounding contact 56 as the magnetic finger 68 enters the workpiece w.

Assuming that the circuit of Fig. 7 is in the condition shown, with the grinding wheel 5' approaching the workpiece a. for the initiation of the grinding operation, it is evident that as the wheel enters the workpiece, the finger 68 moving therewith will also enter the workpiece with a very small air gap between the finger 68 and the inner periphery of the workpiece, see Fig. 2. As this occurs, the inductance of the circuit including the gaging coil 33' is suddenly altered to such an extent that the voltage of the output of the tube 1'! is sufficient to simultaneously energize both relay windings 49' and 50. The engagement of contacts 56 and 51 is so timed that the energization of relay windings 49 and 59 has separated the movable contacts 83, and 84 from the stationary contacts 85 and 86 respectively, as shown in dotted lines, before contacts 85 and 86.are grounded. Consequently, the electromagnets l1 and 29 are maintained in a deenergized condition while the finger 68 remains within the then unreduced workpiece a.

While upon each withdrawal of the finger 68 from the workpiece a, deenergization of the relay windings 49' and 59' permits the movable contacts 83 and 84 to drop back, electromagnets I1 and 29 still remain deenergized, due to the separation of the table controlled contacts 56 and 51. The above described energization of the relay windings 49' and 66' occurs upon each entry of the finger 68 within the workpiece a with the grinding wheel 6 until increase of the internal diameter of the workpiece, 0. reduces the inductance of the circuit of the gaging coil 33 to a predetermined value. That is to say, when the workpiece has been reduced to a predetermined amount, the increased air gap between the finger 68 and the workpiece is such that the output voltage of the tube 11 is not sufficient to energize the relay windings 49' and 59". Consequently, upon the succeeding right hand movement of the table, the electromagnet I1 is energized, due to the engagement between contacts 83 and 85, and the wheel is withdrawn from the work for truing in the manner previously described with reference to Figs. 5 and 6.

The relay winding 50' is so proportioned that it will hold up its movable contact 84 upon being energized by a somewhat lower voltage than the relay winding 49'. Therefore, upon one or more working strokes of the grinding wheel 5- after truing, the energization of relay winding 66' will prevent completion of the circuit of the electromagnet 29, the switch member 26 then having been brought into engagement with its contact 6| by the previous runout of the grinding wheel for truing. However, when one or more strokes of the grinding wheel following the truing operation has reduced the workpiece a, to its predetermined finish size, the increased air gap between the finger 68 and the workpiece prevents energization of the relay winding 50 and the resulting energization of the electromagnet 29 causes final separation of the grinding wheel 5 from the workpiece a. While in, the circuit of Fig. '7, the gaging coil 33' is shown as being mounted with the finger 68, obviously the same results would be obtained with the gaging coil 33 associated with the gaging disk 34a, as shown in Fig. 1,'or with the'stationary core 69 as shown in Fig. 4.

As previously pointed out, the present invention also contemplates the utilization, of variations in value of either the inductance or capacity of the detecting circuit, and there will next be described with reference to Figs. 8 to 11 inclusive, the manner in which variations of ca-' of the workpiece. Referring to Fig. 8, the grinding wheel spindle 6 is shown as carrying a disk 8'! of conducting material, such as carbon, the disk 81 being of exactly the same diameter as the wheel 5. The wheelhead 2 is insulated as indicated, with a lead 98 extending therefrom, the purpose of which will shortly appear. The workholding chuck 1 provides a recess la, in which is received gage ring 89 of conducting material, the gage ring 89 being insulated from the chuck I at 90. The gag'e ring 89 is connected to a collector ring 9! turnable with the chuck I, and a brush 92 bearing on the collector ring 9| has a lead 93 extending therefrom, the purpose of which will shortly appear.

Referring now to Fig. 10, the leads 88 and 93 from the disk 81 and gage ring 89 respectively, are shown as being connected across the ter. minals of the secondary winding 94 of a supply transformer T, the primary winding 95 of which is energized from a suitable alternating current source 96. Consequently, the disk 81 and gage ring 99 are continuously charged, and as the disk 81 moving with the grinding wheel 5 enters within the ring at the end of the grinding stroke, there will be a condenser effect between the disk 81 and gage ring 89. At the beginning of the grinding operation, the internal diameter of the unreduced workpiece a is considerably less than the internal diameter of the gage ring 89,

'as indicated in Fig. 8, so that the capacity of the condenser in the circuit, including the disk 81 and gage ring 89, is at a relatively low value. Obviously, as material is removed from the workpiece by the grinding operation accompanied by traversing of the grinding wheel 5 itself, the air gap between the disk 81 and gage ring 89 will decrease, with a resulting increase of capacity between these members at the end of each cutting stroke of the wheel 6.

Referring again to Fig. 10, there is shown a circuit for utilizing variations of the capacity in the circuit of the secondary winding 94 to directly determine the degree of energization of the electromagnets l1 and 29 controlling the grinding wheel operating mechanism. As shown,'the grid circuit of a thyratron tube 91 is energized from a transformer T, the primary winding 99 of which has one terminal 98a con- :nected to an intermediate point 94a of the secondary winding 94. The other terminal 98b of the primary 98is connected, in parallel, to the respective terminals 94b and 940 of secondary 94, with a resistance 99 in circuit between terminal 98b and the terminal 941) of secondary 94. The terminal 981) is also connected to the disk 81 and gaging ring 89 in the circuit to the secondary winding terminal 940. Thus, the potential across the primary winding 98, and hence between the grid and cathode, is made up of two components having difierent phase angles. That is to say, one component is dependent upon the unvarying value of the resistance 99, while the other component is dependent upon the varying values of capacity in the circuit including the disk 81 and gaging ring 89. Therefore, variations of capacity in the circuit including the gaging ring 89 will directly affect the phase angle of the grid potential, which in turn will determine the amount of current passing through the tube 91.

The plate circuit of the tube 91 includes the secondary winding lllll of a transformer, the primary winding I09 of which is energized from a suitable source IOI. One terminal of the seccontrolled switch member 26, so that either the electromagnet I1, or the electromagnet 29, is also included in the plate circuit, depending on the position of the switch member 26 with respect .to its stationary contacts 58 and GI, as,

previously described. Assuming that the circuit of Fig. 10 is in the condition shown, with the grinding wheel just starting to remove material from the workpiece a, it is evident that the capacity of the circuit including the disk 81 and gaging ring 89 is then at a negligible value, and the phase angle of the grid potential is then such that the amount of current passing through thetube 91 is not great enough to energize the electromagnet I1. Furthermore, at the initiation of the grinding operation on a new workpiece, the air gap between the gage 81 and ring 89, even with the disk 81 entirely within the ring at the end of the grinding stroke, is so great that there is no appreciable passage of current by the tube 91.

As the grinding operation proceeds, each feed of the wheel 5 brings the disk 81 closer to the. ring 89 at the end of a stroke, thereby increas ing the capacity of the circuit including the disk 81 and gaging ring 89. As previously pointed out, the increased capacity of this circuit directly afiects the phaseangle of the grid potential so as to increase the amount of current passed by the tube 91, and when the workpiece a has been reduced to a predetermined roughing size, the current passing through the plate circuit is suflicient to energize the electromagnet I1. Consequently, the wheel 5 is withdrawn from the work for truing, in the manner previously described with reference to Figs. 5 and 6.

Upon the return of the wheel 5 to the workpiece following the truing operation, the electromagnet 29 is thrown into the plate circuit by engagement of the switch member 26 with the contact BI. However, the electromagnet 29 is so wound that it .will not attract its armature '28 until the current in the plate circuit reaches a slightly higher value than the current which previously caused energization of the electromagnet Il. Therefore, the wheel 5 will take one or more cuts so as to further increase the capacity of the circuit including the disk 81 and ring 89. Finally when the workpiece has been ground to its predetermined finished size, the phase angle of the grid potential is such that sufficient current is passed by the tube 91 to fully energize the electromagnet 29, the resulting energization of the electromagnet 29 causing final separation of the grinding wheel 5 from the workpiece a.

Referring now to Fig. 9, there is shown a modified form of gaging condenser utilizing the actual approach of the periphery of the grinding wheel to a predetermined plane, by the crossfeed movement, to obtain the desired variations in the capacity of the gaging circuit. In Fig. 9, a gaging stud I02 is threaded into a bushing I03, which in turn is insulated at I04 from a bracket I05 extending upwardly from a fixed portion of the machine frame. The stud I02 provides a head I00 carrying a micrometer scale E01, and turning of the head in thebushing I03 determines the air gap between the enlarged end of the stud and a disk I08 carried by the upper end of an arm I00. The disk supporting arm I09 is carried by one end of a resilient member IIO shown as a leaf spring, with the other end of the member received in the bracket I05. The stud I02 and the arm I09 provide leads-III and- H2 suitably insulated from the bracket I05, and these leads are adapted to be connected in the circuit of the secondary winding 94 of the-supply transformer in Fig. 10in the same manner as previously. described with reference to the gaging condenser leads 88 and 93.

Normally with the parts shown in the position of Fig. 9, that is at the start of the grinding'operation, the resilient member "0 extends substantially horizontally so that the vertical arm I09 maintains the disk I08 at an appreciable distance from the opposed end of the stud I02. Assumlng then that the leads III and I I2 are connected in circuit with the'secondary winding 94 as shown in Fig. 10, the capacity between the stud I02 and the disk I I I-.wi1l then have such a small value that not enough current will be passed by the tube 91 to energize'the electromagnet I1.

This condition of aflfairs obtains'at the start of the grinding operation and continues as long as there is a gap between the periphery of the grinding wheel 5 and the'rounded surface of a diamond II 3, or other inset of hard material, carried by the lower extremity of the arm I09 below the plane of the resilient supporting'member I I0.

As the grinding proceeds, each operation of the cross-feed mechanism brings the periphery of the grinding wheel 5 nearer to the surface of the diamond II 3, and the bracket I05 carrying the arm I09 is so set that when the work iece a has been reduced to the roughing size, th next succeeding crossfeed of the wheelhead will cause the periphery of the wheel 5 to engage the rounded surface of the diamond I I3. When this occurs, the lower end of the arm I09 is depressed, due to the flexure of the member IIO, thereby swinging the upper portion of the arm toward the stud I02. Due to the relatively much greater distance between the disk I08 and the resilient member IIO, as compared to the distance between the diamond H3 and the member III), .a very slight deflection of the member IIO will move the disk I08 a considerable distance toward the end of the stud 02. When this occurs, the reduced air gap between the disk I08 and the end of the stud I02 the tube 91 will function in substantially the same manner as previously described with reference to Fig. 10, with either the gaging ring 89 and its shiftable disk 81, or the gaging stud I02 and its shiftable disk I08 connected across the secondary 94 of the supply transformer.

Referring now to Fig. 11, there is shown a modified arrangement in which the gaging condenser is included in a receiving circuit adapted to energize the electromagnets I1 and 29, variations in the capacity of the gaging condenser be ing employed to bring the frequency of the receiving circuit in tune with that of an oscillatory exciting circuit when the work is reduced to a predetermined diameter. An oscillatory exciting circuit suitable for this purpose comprises plate and on the filament of the tube H4. The

grid circuit 01' the tube Ill includes a grid leak I I1 in series with a feed back coil IIB inductively related to a coil III! in the plate circuit.

The receiving circuit is coupled to the exciting circuit through a primary winding II9 connected across the terminals of the coil 8' through an adjustable condenser I20, the primary winding I I9 being inductively related to a secondary winding I2I in the receiving circuit. One terminal of the winding I2I is connected, in parallel, to .a grounded condenser I22 and to the gaging condenser represented by the previously described gaging stud I02 and disk I08. The other terminal of the secondary winding I2I is connected to the electromagnet II, while an intermediate.

, point I2Ia of the winding I2I is connected to the electromagnet 29. a

With the table controlled switch member 26 in the position shown, that is, connected to the electromagnet II, it is evident that the natural frequency of the receiving circuit is determined by the combined capacity 01' the condenser I22 and of the gaging condenser, and the inductance of the entire secondary winding I2I combined with that of the electromagnet I'I. However, with the switch member 26 in its other position to connect the electromagnet 29 in the receiving circuit, it is evident that the natural frequency or the receiving circuit will have a difierent value, due to the fact that only a portion of the secondary winding I2I is then included in the receiving circuit. Furthermore, variations in the capacity of the gaging condenser will also vary the frequency of the receiving circuit.

At the start of the grinding cycle, the position of the parts of the gaging condenser is such that there will be a considerable air gap between-the disk I08 and the gaging stud I02, and the capacity of the gaging condenser will have a very low value. Under this condition, the natural fre-.

quency of the receiving circuit is different from that of the exciting circuit, so that not enough current flows in the receiving circuit to energize the electromagnet Il. As the grinding proceeds, the capacity oi! the gaging condenser remains unchanged until the feed of the wheel causes its periphery to engage the diamond H3. When this occurs, the capacity of the condenser suddenly increases, due to the reduction of the air gap between the stud I02 and disk I08, and this increase of capacity causes the frequency 01' the receiving circuit to apprbach that of the exciting "circuit. The frequency of the exciting circuit is initially set so that when the workpiece has been reduced to the roughing diameter, the

increased capacity of the gaging condenser brings the receiving circuit substantially in tune with the exciting circuit, whereupon energization of the electromagnet I! by the increased flow or current in the receiving circuit causes the grinding wheel to be withdrawn for truing.

When the trued grinding wheel 5 is returned to the work forthe finishing cut in the manner previously described, the switch member 26 is then in position to connect the electromagnet 29 in the receiving circuit. Therefore, the natural frequency of thereceiving circuit has a different value than at the start of the grinding operation, due to the fact that only a portion of the secondary winding I2I is included in the reis again out of tune with the exciting circuit when the grinding wheel returns to the work after truing, and not enough current is passed by the receiving circuit to energize the electrosaid workpiece reaches a redetermin ceivingcircuit. As a result, the receiving circuit p ed size magnet 28. Further feed of the wheel 5, however, with the corresponding increase in the capacity of the gaging condenser compensates for the reduced inductance of the secondary winding I2I, and brings the receiving circuit again in 5 tune with the exciting circuit when the workpiece has been reduced to a predetermined .flnished diameter. This results in full energizatlon of the electromagnet 20 and the flnal run out of the table to complete the grinding cycle. 0bviously, the type of gaging condenser shown in Fig. 8 can also be utilized in connection with the circuit arrangement just described with refer;- ence to Fig. 11.

I claim:

1. In a mechanism including a workpiece and a tool for performing a cutting operation on said workpiece, an electrical circuit and means for automatically controlling the progress of the cutting operation in accordance with variations 20 in the impedance of said electrical circuit, with such variations of impedance resulting directly from the magnetic influence of the workpiece on said circuit.

2. In a mechanism including a workpiece and 25 a tool for performing a cutting operation on said workpiece, an electrical circuit and means for automatically controlling the 'progress of the cutting operation in accordance with variations in the inductance of said electrical circuit, with 30 such variations of inductance resulting directly from the magnetic influence of the workpiece on said circuit.

3. In a mechanism including a workpiece and a tool for performing a cutting operation on said workpiece, an electrical circuit and means for automatically controlling the cutting operation in accordance with variations in the impedance of said electrical circuit, with said variations of impedance resulting from changes in the magnetic influence of the workpiece on said circuit due to the removal of material from the workpiece.

4. In a mechanism including a workpiece and a tool for performing a cutting operation on said workpiece, an electrical circuit and means for automatically controlling the cutting operation in accordance with variations in the inductance of said electrical circuit, with said variations of inductance resulting from changes in the magnetic influence of the workpiece on said circuit due to the removal of material from the workpiece. I r

5. In a machine of the class described, the combination with a cutting tool and means to procure a cutting operation between said tool and a workpiece, of an electrical circuit and means responsive to variations in the impedance of said electrical circuit resulting directly from the magnetic influence of the workpiece on said circuit for controlling the cutting operation.

6. In a machine of the class described, the combination with a cutting tool and means to procure a cutting-operation between said tool and a workpiece, of an electrical circuit and 65 means responsive to the value of the impedance of said electrical circuitresulting directly lrom the magnetic influence of the workpiece on said circuit to interrupt the cutting operation when 7. In a machine of the class described, the combination with a cutting tool and means to procure a cutting operation between said, tool and a workpiece, of an electrical circuit and means responsive to the value or the inductance 75.

2,060,261 of said electrical circuit resulting directly from the magnetic influence of the workpiece on said circuit to interrupt the cutting operation when said workpiece. reaches a predetermined size.

8. In a machine of the class described, the combination with a cutting tool and means to procure a cutting operation between said tool and a workpiece, of an electrical circuit and means responsive to the value of the impedance of said electrical circuit as determined by the magnetic influence of said workpiece on said circuit to interrupt the cutting operation when a predetermined amount of material has been removed from said workpiece.

9. In a machine of the class described, the combination with a workholder, a cutting tool, and means to procure a cutting operation between said tool and a workpiece carried by said holder, of a gage movable with respect to said workpiece, without contacting the same, and means responsive to the value of the impedance of an electrical circuit including said gage as determined by the magnetic influence of said workpiece on said circuit to interrupt the cutting operation when the workpiece reaches a predetermined size.

10'. In a machine of the class described, the

combination with a workholder, a cutting tool,

and means to procure a cutting operation between said tool and a workpiece carried by said holder, of a gage movable with respect to said workpiece, without contacting the same, and means responsive to the value of the inductance of an electrical circuit including said gage as determined by the magnetic influence of said workpiece on said circuit to interrupt the cutting operation when the workpiece reaches a predetermined size. 1

11. In a machine of the class described, the combination with a workholder, a cutting tool, and means to procure a cutting operation between said tool and a workpiece carried by said holder, of a gage movable with respect to said workpiece without contacting the same, and means responsive to the value of the impedance of an electrical circuit including said gage to interrupt the cutting operation when the workpiece reaches a predetermined size, said value of impedance being determined by the air gap between said gage and said workpiece due to the removal of material therefrom.

12. In a grinding machine, the combination with a work-holder, a grinding wheel, and means to procure a grinding cycle on a workpiece carried by said holder, of an electrical circuit and means responsive to variations in the impedance of said electrical circuit resulting directly from" the magnetic influence of the work-piece on said circuit to automatically control the progress of the grinding cycle.

13. In a grinding machine, the combination with a work-holder, a grinding wheel, and means to produce a grinding cycle on a workpiece carried by said holder, of an electrical circuit and means responsive to variations in the impedance of said electrical circuit resulting directly from the magnetic influence of the work-piece on said circuit to automatically control the progress of the grinding cycle, said cycle being characterized by temporary separation of the wheel from the workpiece for truing, when the workpiece is reduced to roughing size, and final separation of the wheel from the workpiece when the latter'reaches predetermined finished size.

14. In a grinding machine, the combination with a work-holder, a grinding wheel, and means to procure a grinding cycle on a work-piece carried by said holder, of an electrical circuit and means responsive to variations in the impedance of said electrical circuit resulting directly from the magnetic influence of the work-piece on said circuit to automatically control the progress of the grinding cycle, one value of impedance ca'using temporary separation of thewheel from the workpiece for wheel truing, when the workpiece is reduced to roughing size, and a second value of impedance causing final separation of the wheel from the work-piece when the latter is reduced to predetermined finished size.

15. In a machine of the class described, a grinding element adapted to progressively grind a work-piece, transverse feed means therefor, control means adapted to alter said feed, and a calipering device comprising a variable impedance unit arranged within the range of influence of the work-piece whereby the impedance thereof varies as a function of the spacing of the workpiece therefrom, and means responsive to variations in said impedance to actuate said control means when the spacing of said work-piece reaches a predetermined .value.

1 16. In a grinding machine, a grinding element having a transverse feed for progressively grinding a work-piece toa predetermined size, means to alter said feed, an electro-magnetic calipering device within the range of magnetic influence of the work-piece but normally out of contact therewith, and means responsive to changes in the magnetic influence of said work-piece produced by an increase in the air gap between said workpiece, and said calipering device as the piece is progressively ground, said last means being adapted to actuate said first means for altering the feed at predetermined points in the grinding operation.

1'7. In a grinding machine, a grinding element having a transverse feed for progressively grinding a work-piece to a predetermined size, means to alter said feed, an electro-magnetic calipering device so disposed with respect to the work-piece that a portion of the work-piece and the air gaps between the work-piece and said device are included in the magnetic circuit thereof whereby changes in said air gaps alter the impedance of said device to alternating currents, and means responsive to such changes in impedance to actuate said flrst means at predetermined points in the grinding operation.

I8. In a grinding machine, a grinding element having a transverse feed for progressively grinding a work-piece to 'a predetermined size, means to alter said feed, and a calipering device comprising an electromagnetic unit having a magnetizing coil and a core, said unit being disposed so that the work-piece is included in its magnetic circuit whereby the reluctance of said circuit is determined by the gap between said core and saidwork-piece, an alternating current circuit including said coil, the impedance of said last circuit varying as a function of said gap, and means responsive to changes in the impedance of said circuit to actuate said first means at predetermined points in the grinding operation.

19. In a grinding machine, the combination with a work-holder, a grinding element and means to procure a grinding operation between said element and a work-piece carried by said holder, of an electro-responsive gage movable within the range of electrical influence of said work-piece without contacting the same, an alternating current circuit including said gage and ,means responsive to variations in the impedance of said circuit resulting from the electrical inwith a work-holder, a grinding element and means to procure a grinding operation between said element and a work-piece carried by said holder, of an electro-responsive gage movable within the range of electrical influence of said work-piece, without contacting the same, an alternating current circuit including said gage and means responsive to variations in the impedance of said circuit resulting from the electrical influence of the work-piece on said gage for interrupting the grinding operation when the work-piece reaches a predetermined size.

21. In a grinding machine, the combination with a work-holder, a grinding element and means to procure a grinding operation between said element and a work-piece carried by said holder, of an electromagnetic gage movable within the range of magnetic influence of said work-piece, without contacting the same, an alternating current circuit including said gage and means responsive to variations in the impedance of said circuit resulting from the magnietic influence of the work-piece on said gage for automatically controlling the grinding operation between said work-piece and said element.

22. In a grinding machine, the combination with a work-holder, a grinding element and means to procure a grinding operation between said element and a-wvork-piece carried by said holder, of an electromagnetic gage movable within the range of magnetic influence of said workpiece, without contacting the same, an alternating current circuit including said gage and means responsive to variations in the impedance of said circuit resulting from the magnetic influence of the work-piece on said gage for interrupting the grinding operation when the work-piece reaches a predetermined size.

23. In a grinding machine, the combination with a work-holder, a grinding element and means to procure a grinding operation between said element and a work-piece carried by said holder, of an electromagnetic gage movable within the range of magnetic influence of said workpiece, without contacting the same, an alternating current circuit including said gage and means responsive to variations in the impedance of said circuit resulting from the magnetic influence of the work-piece on said gage for temporarily separating the element from the work-piece, for truing, when the work-piece is reduced to roughing size and for finally separating said element from the work-piece when the latter is reduced to finished size.

' HAROLD L. BLOOD. 

